1. Field of the Invention
The present invention relates to stabilizers for polymers and other organic materials. More particularly, the present invention relates to stabilizers for polymers or other organic materials that are phosphorus-containing molecules or oligomers that do not act as xenoestrogens.
2. Description of Related Art
Phosphorus-containing antioxidants, such as, phosphites, have been used as stabilizers in organic materials, such as, rubber, plastics, oils, and the like. The fourth edition of “Plastic Additives” by Gachter and Muller discusses in great detail the stabilization of plastics and polymers by commercialized phosphites, such as, tris(nonylphenyl)phosphite (TNPP) and tris(2,4-di-t-butylphenyl)phosphite. TNPP is the primary low cost liquid phosphite stabilizer used in the plastics and rubber industry. Recently, however, plastic and rubber manufacturers have been reluctant to utilize TNPP in their formulations owing to concerns that TNPP may be a xenoestrogen (foreign estrogen). Many of these concerns were raised recently in Colburn, T. et al., Our Stolen Future, Dutton (1996) and related articles. In this regard, xenoestrogens are suspected of being hormonally active in developing organisms.
Non-polymeric phosphite compounds are disclosed in U.S. Pat. No. 5,290,747 as primary catalysts for the formation of Nylon 6. The generic structures of these disclosed phosphites are represented by generic structure I (where n>5).

With regard to non-polymeric phosphite stabilizers, two general classes of phosphites known in the prior art can be represented by structures II and III.
wherein R is H or CH3 and X is oxygen, sulfur, nitrogen, and the like. Included in generic structure II is commercially available Irgaphos 38 (where R═CH3 and X═H) described in European Patent EP-511156A2. The authors describe the phosphites listed in this patent as stabilizers for organic materials. All the stabilizers listed in EP 511156 have structures where R is represented as a methyl group. Much of the variation of the group X includes functionalized heteroatoms, such as, nitrogen, sulfur, oxygen, or functional groups such as cyano, trifluoromethyl, hindered amines, etc. The authors also describe structures wherein R═CH3 and X is an alkyl or aralkyl group.
Japanese Patent 54163938 describes the improved thermal stability of PVC and ABS polymers containing compounds of structure II where R═H and X is an ethylene glycol.
Japanese Patent 55000747 describes a similar composition wherein R═CH3.
German patent DE2709528 describes a stabilizer for plastics, such as, polypropylene, where R═H and X contains a second phosphite in a spiral arrangement.
British patent GB1180398 describes phosphites (where R═H and the entire group attached to X and including X is a tert-butyl group) used as thermal stabilizers for SBR or ABS rubber.
German patent DE4202276 describes a compound related to Irgaphos 38 (where R═H and X═H) that is used as a stabilizer for polyolefins.
Japanese Patent JP03025437 describes a butyl sulfone derivative (where R═H and X═SO2-butyl) used in silver halide color photographic materials to prevent fading of color images.
Japanese patent JP59004629 describes a phosphite linked to another phosphite structure through an ether linkage (R═H and X═O). This phosphite is used as a photochemical and thermal stabilizer for polymer compounds.
German patent DE19520337 describes phosphite compounds (R═H, CH3 and X═O) used to stabilize organic materials, such as, polyolefins, lubricants, etc. against oxidative, thermal or photochemical degradation.
A second general class of non-polymeric phosphites is represented by generic structure III. Phosphites within generic structure III are materials wherein the bis(2,4-di-tert-butylphenol)phosphite groups are joined symmetrically or non-symmetrically to a linkage group Y.
